Method of making plastic container having a deep-inset base

Abstract

A method of plastic container having a deep inset base of the type that has a standing ring for supporting the container on a flat surface includes steps of molding a container blank having a standing ring and a base projection portion that is formed beneath the standing ring and relatively displacing the base projection portion upwardly with respect to the standing ring until the base projection portion is positioned above the standing ring. An improved plastic container having a deep inset base is also disclosed.

What is claimed is: 
     
       1. A method of making a plastic container having a deep inset base comprising steps of:
 molding a plastic preform into an intermediate plastic container blank having a container bottom comprising a standing ring and a base projection portion formed beneath standing ring with the container blank in an upright position, the base projection portion having a lowermost end wider than an opposite end thereof, said opposite end being proximate to said standing ring, so that a substantially straight sidewall of the base projection portion is angled outwardly toward said lowermost end with respect to a longitudinal axis of the container blank, wherein a maximum diameter of the base projection portion is within a range of about 80% to about 110% of a maximum diameter of a remainder of the container blank; and 
 relatively displacing the base projection portion upwardly with respect to the standing ring so as to convert the base projection portion into a central push-up area positioned inside the container bottom, the substantially straight sidewall of the base projection portion thereby forming an upstanding container bottom sidewall portion having an angle of about 0° with respect to said longitudinal axis. 
 
     
     
       2. A method of making a plastic container according to  claim 1 , wherein said upstanding container bottom sidewall portion has a height that is within a range of about 0.35 inch to about 1.2 inch. 
     
     
       3. A method of making a plastic container according to  claim 1 , wherein said upstanding container bottom sidewall portion defines a continuous, inwardly facing annular ring. 
     
     
       4. A method of making a plastic container according to  claim 1 , wherein said upstanding container bottom sidewall portion has an average wall thickness that is within a range of about 0.018 inch to about 0.011 inch. 
     
     
       5. A method of making a plastic container according to  claim 4 , wherein said average wall thickness is about 0.014 inch. 
     
     
       6. A method of making a plastic container according to  claim 1 , wherein said maximum diameter of the base projection portion is about 95% of said maximum diameter of the remaining container blank. 
     
     
       7. A method of making a plastic container according to  claim 1 , wherein said substantially straight sidewall is symmetrically shaped about a circumference of the base projection portion so as to define a substantially straight annular wall. 
     
     
       8. A method of making a plastic container according to  claim 1 , wherein said substantially straight sidewall has a length that is within a range of about 75% to about 115% of a height of said upstanding sidewall portion. 
     
     
       9. A method of making a plastic container according to  claim 1 , wherein said relative displacement stretches plastic material of said base projection portion. 
     
     
       10. A method of making a plastic container according to  claim 1 , wherein said molding comprises applying pressurization to said preform within a mold assembly, and wherein said relative displacement is initiated while the intermediate container blank remains pressurized relative to ambient pressure. 
     
     
       11. A method of making a plastic container according to  claim 10 , wherein said relative displacement stretches plastic material of said base projection portion. 
     
     
       12. A method of making a plastic container according to  claim 10 , wherein said remaining pressure is at least 50% of a maximum pressurization that occurs during said molding. 
     
     
       13. A method of making a plastic container according to  claim 10 , wherein said remaining pressure is at least 260 psi.